In particular, the present invention relates to a dispenser of the type comprising a containment body with substantially axial-symmetric geometry, internally hollow and able to be inserted in the neck of a bottle.
The containment body is fastened to a threaded ring nut which is screwed onto the neck of a bottle.
In particular, the containment body comprises an annular portion facing an annular portion of the ring nut and fastened thereto.
The containment body is provided in a first end of an orifice for the entry of the liquid product present in the bottle. Said orifice is opened or closed by a valve, slidably movable within the containment body, in particular within a dosing chamber included therein.
The dosing chamber is defined by the space present between a piston, guided by an internally hollow stem, able to slide within the containment body and the bottom portion (where the orifice is positioned) of the containment body.
Between piston and stem are present means for opening and closing the inner cavity of the stem in such a way as selectively to place in fluid communication the interior of the stem with the dosing chamber.
The stem is guided in its travel by a retaining ring, integral with the containment body, which also serves as an abutment for the travel of the piston.
In other words, the retaining ring defines the upper limit of the dosing chamber, preventing the piston from being able to exit from the dosing chamber itself.
When the piston creates an overpressure within the dosing chamber, the cavity of the stem is in fluid communication with the dosing chamber and the fluid present in the dosing chamber rises along the stem and is dispensed by a spout associated therewith.
In this configuration, the valve is lowered and occludes the aforementioned orifice because of the overpressure in the dosing chamber.
When the piston creates a vacuum within the dosing chamber the cavity of the stem is not in fluid communication with the dosing chamber and fluid is moved from the bottle into the dosing chamber.
In this configuration, the valve is raised and leaves open the aforementioned orifice because of the vacuum in the dosing chamber.
In this type of dispenser, the sliding of the piston within the containment body takes place contrasting the action of a spring whose function is to maintain the piston in raised position.
In particular, when a compression action is exercised on the stem, the piston slides within the dosing chamber, reducing its dimensions and hence creating an overpressure within it.
Ceasing the compression action on the stem, the aforementioned spring brings the piston back to the raised position, expanding the dimensions of the dosing chamber and hence creating a vacuum therein.
The pressure action on the stem is exerted on the dispensing spout located at the upper end of the stem and in fluid communication therewith to dispense into the external environment the liquid contained in the bottle.
Clearly, at each dispensing action a volume of air equal to the dispensed liquid must enter the bottle to maintain a pressure equilibrium between the interior of the bottle and the outside atmosphere.
For this purpose, in prior art dispensers between the fastening ring nut and the dispensing spout that emerges from it there is a fluid blow-by, i.e. an inlet passage for air, in such a way that air from the external environment can flow into passages created within the containment body.
In particular, such passages assure that the air that blows by between spout and ring nut can reach a hole drilled on the outer surface of the containment body that is located inside the bottle.
Said passages place in fluid communication the external environment with the aforementioned hole when the piston is in lowered position, i.e. when the piston is returning upwards within the dosing chamber.
In this way, the liquid drawn from the bottle in the dosing chamber is replaced by air injected into the bottle.
When the piston is in raised position, the openings occlude the fluid communication between the external environment (i.e. between the air inlet) and the interior of the bottle (i.e. the hole drilled in the containment body).
The prior art dispensers described above present some drawbacks.
In particular, under heavy water spray conditions, e.g. under a shower, a film of water is created that coats the upper part of the dispenser (i.e. the part bearing the spout) directly exposed to the water spray.
Therefore, when the dispenser is operated, through the blow-by between spout and ring nut water is also injected into the containment body, in addition to air.
The water that enters the containment body follows the same path as air and, through the aforementioned openings, it reaches the interior of the bottle where it mixes with the liquid contained therein.
This causes the dilution with water of the liquid contained in the bottle which, following prolonged uses of the dispenser, may be found heavy and hence unacceptable.
Some prior art dispensers have overcome this problem by providing slidable, liquid-tight couplings between ring nut and spout. To prevent liquid blow-by, the tolerances between the two coupled elements must be minimal, but this has the disadvantage of risking the seizing of the parts, unless extreme precision is assured in the dimensioning of the mutually sliding components or an additional connecting component is used.
An additional drawback, which often occurs among prior art dispensers, is the possible pollution of the product because of possible corrosive phenomena that may involve the metal parts in contact with the product to be dispensed, in particular the return spring.
In the prior art, there are systems that have partly overcome this drawback, placing the spring outside the work chamber. There are multiple solutions, according to the different purposes to be achieved. Each of the existing solutions, however, is subject to limitations or cause particular drawbacks.